Many types of binoculars (i.e., dual refractory telescopes) are known, commercially available and include, among other things, two binocular tubes, each with an eyepiece and an objective assembly associated therewith. Relative positioning of the corresponding eyepieces and objective assemblies and correction for the vision of an individual user results in the observation of a clear and sharp image by the user (i.e., "focus"). Traditionally, individual focus binoculars have been focussed by a user through rotation of the eyepiece or the objective assembly. Such rotation may result in misalignment of the mechanical and optical axes of either or both binocular tubes, and parallax may, in turn, result from such misalignment.
Prior art binoculars generally employ either center focus or individual focus mechanisms. Center focus is achieved by a user through the adjustment of a single knob, typically located in the central portion of the structure (i.e., the bridge between the two binocular tubes) at or near the eyepiece end thereof. In contrast, individual focus is achieved by a user through dual adjustment features, each typically located in a contacting relationship with a corresponding binocular tube. U.S. Pat. No. Des. 292,412 is directed to eyepiece-rotational, individual focus binoculars exhibiting a hinge-like bridge structure for storage compactness.
U.S. Pat. No. 4,346,960 issued to Lehrmund et al. discusses binoculars having a first "ganged" control to axially adjust both objectives simultaneously and a second "single" control to axially and independently adjust one objective. More specifically, the single control provides for adjustment of the objective assembly located within one binocular tube to the exclusion of adjustment of the objective positioned in the other tube. Binoculars described in this patent exhibit a double-jointed central portion.
Similarly, U.S. Pat. No. 4,630,901 issued to Altenheiner et al. discusses binoculars having a dual knob control structure, where one knob is capable of joint focusing of both optical elements (i.e., combinations of corresponding eyepieces and objective assemblies), and the other knob is capable of adjusting an individual objective assembly to correct for defects in a user's vision. Longitudinal adjustment of objective position is employed in the patented apparatus. In addition, these patented binoculars exhibit a hinged central portion.
U.S. Pat. No. 4,989,963 issued to Farnung et al. also discusses a combination joint adjust/individual adjust mechanism for use with binoculars to permit them to be focused by a user employing only one hand. For this purpose, a single control knob is provided. The joint adjust mechanism is engaged when two setting rings are in a coupled configuration, while individual focus is implemented when the setting rings are uncoupled. Longitudinal adjustment of objective assembly position is also employed in focusing these patented binoculars. Individual adjustment of both objectives cannot be conducted at the same time, however. In addition, the prior art binoculars exhibit an articulated central portion.
U.S. Pat. Nos. 4,080,042 issued to Hornschu et al.; 4,080,043 issued to Altenheiner et al.; 4,087,153 issued to Hengst; 4,436,387 issued to Shimizu; and 4,998,357 issued to Farnung et al. appear to discuss central, but not individual, focus binocular designs. Some of these prior art apparatus exhibit a hinged, foldable or otherwise collapsible central portion.